熱電材料是能夠將熱能與電能互相轉換的綠色能源材料，常被用於廢熱回收及局部致冷等應用，其製備的熱電元件具有安靜、反應快速等特色。傳統的熱電元件係採用以熔煉長晶或粉末冶金等方法製備之熱電塊材，切割成小尺寸的熱電端腳後，再與金屬導線以串聯方式焊接於陶瓷基板上，形成一發電或致冷元件。此種製程由於切割及組裝方式的限制，容易造成材料浪費及模組空間無法完整利用，製造成本高昂且模組功率輸出無法最佳化。本研究將碲化鉍系熱電粉末摻雜適當的溶劑與黏結劑混合成熱電漿料，在選定的金屬與高分子基板上以模板印刷製程刷塗特定厚度之熱電厚膜，並透過壓力與溫度的調整來提昇印刷型熱電厚膜的性質。接著再以熱壓製程將P型與N型熱電厚膜組裝成熱電元件，利用熱壓製程中產生的介金屬化合物接合熱電厚膜材料與金屬電極以簡化模組組裝製程。另外，在熱電模組設計方面，我們以模擬軟體評估金屬電極寬度與接合方式對熱電模組功率輸出之影響，提供後續熱電厚膜模組製備及改良的方向。本實驗所製備之熱電厚膜其功率因子可達11.3 μW/cmK2，熱電厚膜模組可在17.7度的溫差下得到約9.7 μW 的最佳功率輸出，換算成模組效率因子為0.63 μW/cm^2∙K^2。

Thermoelectric generation devices are able to convert waste heat into electricity. A typical thermoelectric module consists of paired p- and n-type semiconductor pellets that were sandwiched in between two ceramic plates. Generally, these tiny pellets are joined to metallic conductors on the ceramic plates by soldering. The whole fabrication process including pellet dicing, barrier plating and electrode soldering indeed is very time-consuming and costly. In this study, we present a printing-based process to prepare bismuth telluride thick films on a flexible substrate and demonstrate a solder-free process to make a generation module by connecting thermoelectric film and metallic electrode. Bismuth telluride based compounds were ground into fine powders and mixed with organic binders and solvent. The mixture was coated on a substrate by screen-printing and subsequently sintered using a hot-press technique. The p-type Bi-Sb-Te film exhibits a thermoelectric power factor of 11.3 μW/cmK2 at room temperature. To form a thermoelectric module, the contacting electrodes were directly joined to the printed film by forming a layer of intermetallic compound at the contact region through adjustment of sintering pressure and temperature. The thick film module can achieve matching load output power of 9.7 μW under a temperature difference of 17.7 K, and have the TE efficiency factor about 0.63 μW/cm^2∙K^2. The effect of film and contact properties on the performance of thermoelectric modules will be modeled and experimentally evaluated.

[1] Snyder, G. J., & Toberer, E. S., Complex thermoelectric materials. Nature Materials, 7, 105-114. (2008)
[2] Glatz, W., Muntwyler, S., & Hierold, C., Optimization and fabrication of thick flexible polymer based micro thermoelectric generator. Sensors and Actuators A: Physical, 132, 337-345. (2006)
[3] Strasser, M., Aigner, R., Lauterbach, C., Sturm, T. F., Franosch, M., & Wachutka, G., Micro-machined CMOS thermoelectric generators as on-chip power supply. Sensors and Actuators A: Physical, 114, 362-370. (2004)
[4] Glatz, W., Schwyter, E., Durrer, L., & Hierold, C., Bi2Te3-based flexible micro thermoelectric generator with optimized design. Journal of Microelectromechanical Systems, 18, 763-772. (2009)
[5] Navone, C., Soulier, M., Testard, J., Simon, J., & Caroff, T., Optimization and fabrication of a thick printed thermoelectric device. Journal of Electronic Materials, 40, 789-793. (2011)
[6] Schwyter, E., Glatz, W., Durrer, L., & Hierold, C., Flexible micro thermoelectric generator based on electroplated Bi2+ xTe3− x. DTIP 2008, April. Symposium on 46-48. IEEE. (2008)
[7] Chen, A., Madan, D., Wright, P. K., & Evans, J. W., Dispenser-printed planar thick-film thermoelectric energy generators. Journal of Micromechanics and Microengineering, 21, 104006. (2011)
[8] Navone, C., Soulier, M., Plissonnier, M., & Seiler, A. L., Development of (Bi,Sb)2(Te,Se)3-based thermoelectric modules by a screen-printing process. Journal of Electronic Materials, 39, 1755-1759. (2010)
[9] Cao, Z., Koukharenko, E., Torah, R. N., Tudor, J., & Beeby, S. P., Flexible screen printed thick film thermoelectric generator with reduced material resistivity. In Journal of Physics: Conference Series, 557, 012016). (2014) IOP Publishing
[10] Wang, Z., Chen, A., Winslow, R., Madan, D., Juang, R. C., Nill, M., Evans J W & Wright, P. K., Integration of dispenser-printed ultra-low-voltage thermoelectric and energy storage devices. Journal of Micromechanics and Micro-engineering, 22, 094001. (2012)
[11] Madan, D., Chen, A., Wright, P. K., & Evans, J. W., Dispenser printed composite thermoelectric thick films for thermoelectric generator applications. Journal of Applied Physics, 109, 034904. (2011)
[12] We, J. H., Kim, S. J., Kim, G. S., & Cho, B. J., Improvement of thermoelectric properties of screen-printed Bi2Te3 thick film by optimization of the annealing process. Journal of Alloys and Compounds, 552, 107-110. (2013)
[13] Madan, D., Wang, Z., Chen, A., Juang, R. C., Keist, J., Wright, P. K., & Evans, J. W., Enhanced performance of dispenser printed MA n-type Bi2Te3 composite thermoelectric generators. ACS Applied Materials & Interfaces, 4, 6117-6124. (2012)
[14] Bahk, J. H., Fang, H., Yazawa, K., & Shakouri, A., Flexible thermoelectric materials and device optimization for wearable energy harvesting. Journal of Materials Chemistry C, 3, 10362-10374. (2015)
[15] Jo, S. E., Kim, M. K., Kim, M. S., & Kim, Y. J., Flexible thermoelectric generator for human body heat energy harvesting. Electronics Letters, 48, 1015-1017. (2012)
[16] Weber, J., Potje-Kamloth, K., Haase, F., Detemple, P., Völklein, F., & Doll, T., Coin-size coiled-up polymer foil thermoelectric power generator for wearable electronics. Sensors and Actuators A: Physical, 132, 325-330. (2006)
[17] Kim, M. K., Kim, M. S., Lee, S., Kim, C., & Kim, Y. J., Wearable thermoelectric generator for harvesting human body heat energy. Smart Materials and Structures, 23, 105002. (2014)
[18] Yang, J., Aizawa, T., Yamamoto, A., & Ohta, T., Effect of processing parameters on thermoelectric properties of p-type (Bi2Te3)0.25(Sb2Te3)0.75 prepared via BMA–HP method. Materials Chemistry and Physics, 70, 90-94. (2001)
[19] Venkatasubramanian, R., Siivola, E., Colpitts, T., & O'quinn, B., Thin-film thermoelectric devices with high room-temperature figures of merit. Nature, 413, 597-602. (2001)
[20] LeBlanc, S., Yee, S. K., Scullin, M. L., Dames, C., & Goodson, K. E., Material and manufacturing cost considerations for thermoelectrics. Renewable and Sustainable Energy Reviews, 32, 313-327. (2014)
[21] Chen, W. J. & Liao, C. N., A study of electrical properties of Sn63Pb37 and Sn95.5Ag4Cu0.5 solder joint in thermoelectric module. 國立清華大學碩士論文, p.68 (2006)
[22] Lan, Y. C., Wang, D. Z., Chen, G., & Ren, Z. F., Diffusion of nickel and tin in p-type (Bi, Sb)2Te3 and n-type Bi2(Te, Se)3 thermoelectric materials. Applied Physics Letters, 92, 101910. (2008)
[23] Hayashi, S. F., Nakamura, T., Kageyama, K., & Takagi, H., Monolithic thermoelectric devices prepared with multilayer co-fired ceramics technology. Japanese Journal of Applied Physics, 49, 096505. (2010)
[24] Funahashi, S., Nakamura, T., Kageyama, K., & Ieki, H., Monolithic oxide–metal composite thermoelectric generators for energy harvesting. Journal of Applied Physics, 109, 124509. (2011)
[25] https://en.wikipedia.org/wiki/Hall_effect (Wikipedia-Hall effect)
[26] Yadava, Y. P., & Singh, R. A., On the electrical transport in nickel telluride. Journal of Materials Science Letters, 4, 1421-1424. (1985)